Recently, the spreading and maturing of Internet technology and the resultant growth of business and personal applications has fueled demand for bandwidth and services in both telecommunications and data communications. Fiber optic communications systems—and in particular Dense Wavelength Division Multiplexed (DWDM) fiber optic communications systems—have become a key component in many solutions to this demand.
Dense Wavelength Division Multiplexing technology allows data signals from different sources to be simultaneously transmitted on one single optical fiber, where each signal is carried on its own separate light wavelength. As is known, the signal sources can be Synchronous Optical Network (SONET) or Synchronous Digital Hierarchy (SDH) data, Internet (IP) data, Asynchronous Transfer Mode (ATM) data, Fiber Channel data or others.
As a result of this DWDM technology, greater bandwidth can be provided in a single optical fiber. For example, if OC-192 SONET signals are multiplexed and transmitted on a 50 GHz spaced DWDM system across the whole C and L transmission band, each fiber can deliver 1.6 trillion bits of data per second. As a result of this enormous capacity, DWDM is viewed as a solution to the “fiber exhaust” problem and is believed to be an essential component of future all-optical networks.
Since individual wavelengths (optical channels) are densely packed spectrally in DWDM systems, operations performed on individual optical channel requires functions such as filtering, demultiplexing, multiplexing and coupling. Devices that perform these functions on the wavelength domains are essential to DWDM networks. Such devices include for example, optical filters, gain equalizers, wavelength blockers, and wavelength selective switches, among others.
Another important device used in such systems employing dense channel spacings is an optical interleaver. An optical interleaver segregates a group of channels into odd and even sets with doubled channel spacing. Given its importance to DWDM optical networks, a continuing need exists for optical interleavers exhibiting improved characteristics.